FIRST EDITIONS CONTAINING THE FIRST ANNOUNCEMENT OF JANSKY'S DISCOVERY OF RADIO ASTRONOMY. This scientific breakthrough was of great significance to astronomers, as it would now be able to receive and interpret microwaves, which could penetrate the dust clouds that had always obscured light waves and views from ordinary telescopes. Jansky's most important paper is included in vol.21, in which he concludes that the electromagnetic waves of unknown origin originate from a fixed terrestrial source, possibly at a point in the Milky Way.[With:] Second copies of vols. 20 and 21. (5)